[es6] Initial steps towards a correct implementation of IsCallable.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 3a98fcb18b901460715975b09b93b911dc981af8..f1f29d85458102d4d553fb8dd38439d84691d32f 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -5611,32 +5611,33 @@ Condition LCodeGen::EmitTypeofIs(LTypeofIsAndBranch* instr, Register input) {
     final_branch_condition = not_zero;
 
   } else if (String::Equals(type_name, factory->function_string())) {
-    STATIC_ASSERT(NUM_OF_CALLABLE_SPEC_OBJECT_TYPES == 2);
     __ JumpIfSmi(input, false_label, false_distance);
-    __ CmpObjectType(input, JS_FUNCTION_TYPE, input);
-    __ j(equal, true_label, true_distance);
-    __ CmpInstanceType(input, JS_FUNCTION_PROXY_TYPE);
+    // Check for callable and not undetectable objects => true.
+    __ movp(input, FieldOperand(input, HeapObject::kMapOffset));
+    __ movzxbl(input, FieldOperand(input, Map::kBitFieldOffset));
+    __ andb(input,
+            Immediate((1 << Map::kIsCallable) | (1 << Map::kIsUndetectable)));
+    __ cmpb(input, Immediate(1 << Map::kIsCallable));
     final_branch_condition = equal;
 
   } else if (String::Equals(type_name, factory->object_string())) {
     __ JumpIfSmi(input, false_label, false_distance);
     __ CompareRoot(input, Heap::kNullValueRootIndex);
     __ j(equal, true_label, true_distance);
-    __ CmpObjectType(input, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, input);
+    STATIC_ASSERT(LAST_SPEC_OBJECT_TYPE == LAST_TYPE);
+    __ CmpObjectType(input, FIRST_SPEC_OBJECT_TYPE, input);
     __ j(below, false_label, false_distance);
-    __ CmpInstanceType(input, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
-    __ j(above, false_label, false_distance);
-    // Check for undetectable objects => false.
+    // Check for callable or undetectable objects => false.
     __ testb(FieldOperand(input, Map::kBitFieldOffset),
-             Immediate(1 << Map::kIsUndetectable));
+             Immediate((1 << Map::kIsCallable) | (1 << Map::kIsUndetectable)));
     final_branch_condition = zero;
 
 // clang-format off
 #define SIMD128_TYPE(TYPE, Type, type, lane_count, lane_type)       \
   } else if (String::Equals(type_name, factory->type##_string())) { \
     __ JumpIfSmi(input, false_label, false_distance);               \
-    __ movp(input, FieldOperand(input, HeapObject::kMapOffset));    \
-    __ CompareRoot(input, Heap::k##Type##MapRootIndex);             \
+    __ CompareRoot(FieldOperand(input, HeapObject::kMapOffset),     \
+                   Heap::k##Type##MapRootIndex);                    \
     final_branch_condition = equal;
   SIMD128_TYPES(SIMD128_TYPE)
 #undef SIMD128_TYPE